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Date: Wed, 10 Jan 2024 11:35:02 +0100 (CET)
From: Jozsef Kadlecsik <kadlec@netfilter.org>
To: David Wang <00107082@163.com>
cc: ale.crismani@automattic.com, xiaolinkui@kylinos.cn, pablo@netfilter.org, 
    linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org
Subject: Re: Performance regression in ip_set_swap on 6.1.69
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On Wed, 10 Jan 2024, David Wang wrote:

> I confirmed this on 6.7 that this was introduced by commit 
> 28628fa952fefc7f2072ce6e8016968cc452b1ba with following changes:
> 
> 	 static inline void
> 	@@ -1397,6 +1394,9 @@ static int ip_set_swap(struct sk_buff *skb, const struct nfnl_info *info,
> 		ip_set(inst, to_id) = from;
> 		write_unlock_bh(&ip_set_ref_lock);
> 	 
> 	+       /* Make sure all readers of the old set pointers are completed. */
> 	+       synchronize_rcu();
> 	+
> 		return 0;
> 	 }
> 
> synchronize_rcu causes the delay, and its usage here is very confusing, 
> there is no reclaimer code after it.

As I'm seeing just the end of the discussion, please send a full report of 
the problem and how to reproduce it.

Best regards,
Jozsef
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